AJ That's why these simple mass balances that Dbacque and I have both experience with and pictured do work and the work every time if it is control surface flutter. Takes maybe a half hour at most to make up and only one small hole in the surface. If that does not cure then simple move on to the elevators or rudder. But dude your airplane is highly suspect for aileron flutter. Many of the old Bridi pattern types had this problem because the aileron stock selected in the kits was simply to light and flexible.

One small hole is all it takes and if you screw around with a bunch of so called fixes sooner or later your airplane is not going recover when you pull that throttle off and its history.

OK now structural flutter is an entirely different matter and normally that is very obvious. This is not what you described AJ in the first airplane that you described as the subject of this thread. Dude I am willing to bet three burned out glow plugs aginst a stale glazed donut that the subject airplane is experiencing aileron flutter. Simple to find out as dbacque and I described. If I am wrong please post back and collect the bet:cool: I hate stale glazed donuts anyway!

John

Aj, has this problem just recently start or has it been a problem since day one? Might try one thing simple, replace current aileron servo, with a new one, hopefully one with a ball bearing on the output shaft, Good Luck, Bob.

(scale only 4 me) your right about this. I like to keep the speed up. :):)
I like to do problem solving. So this makes a good project for me.

All the hinge lines on all the control surfaces are sealed with monokote.

(JohnBuckner) is the distance critical that the weight has to be in front of the hinge line? Is there a optimum length?

This is what you get when a Trader Talk troll puts their nose into some Tech talk.
A response that was as good as saying, try not flying.
Stupendous.

Without pictures of the OPs set up we are just not able to offer any real suggestions. I bet a picture of all linkages inside and outside the airplane would get valuable suggestions. My bet is that the mechanical setups are off.

^This^
Speed is a direct cause of flutter. What size engine do you have. Many people think you can never have enough and then wonder why their overpowered plane crashes. Many years ago I did flutter analysis at Boeing and by the time the design got around to us the only thing we could do was either limit the speed of the aircraft or increase the wing skin thus increasing it's strength. You have one servo driving two control surfaces that are large than the original design. You are not using hinges instead relying on the covering to provide an adequate hinge. I assume you still use rubber bands to hold the wing on - how many? 10?
Flutter can be a real killer of airplanes. Its primary source are the forces caused by excessive speed.

While speed is a contributing factor is is not the only cause for flutter. For the most part our models are quite overbuilt. When talking about models the most common cause of flutter is poor linkage setup. The OP could have a long servo arm and short control horn, play in the linkage, inadequate servo power, flexing control surfaces and a few other things. Pictures would be very helpful. BTW Q500 airplanes used to have strip ailerons, the main reason why ailerons have been reduced in size is for drag reduction although a side benifit is less odds of flutter. The OP needs to,publish pictures in order to get accurate feedback.

time to redesign things then,, shorten up those surfaces and rip it,, have fun ;)

Wow, solved :confused::confused:

I wouldn't say that counterweighting is always the answer. If any part of the linkage isn't stiff, that's where I always start. Arrow straight push rods, heavy duty linkages, no play in the clevise/horn connection. You should not have any play or flex when you try to move the control surface by hand.

Spotting which surface is fluttering is often impossible. I saw it in my old Goldberg Extra 300 shortly before the stab exploded and once again when the light was just right on the aileron of the Hots. Check all surfaces for slop and flex. Check how much you can twist the ailerons.

As for geometry and mass of the counterweight, I made up a set with just a guess. Good old That Looks About Right. Worked but as I mentioned, after a few flights I finally got another flutter. Replaced the weights with the next size up and that was that. I also guessed where to put it on the aileron. Since the root was very solid and the aileron stock was a bit flexible, I put it out towards the wing tip as shown.

That was the 6th Hots I'd built through the years but the first one with so many flutter problems. Solving it was great fun.

Dave

Ahh great Morning just back from the field spent this day over at the controlline circle side and did new maiden for one of the fellas and some good flights on my old magician. Always makes me feel rejuvenated going back over to the RC side:cool:

AJ the answer is no the distance is no more critical than the weight. Somewhere around a half ounce and 1 to 1.5 inch forward of the hinge line will be well under 100% surface balance, actually more like 15, 20% and its enough to move the flutter threshold higher than the speeds you need to fly at..

Actually mass balance is a very simple diagnostic tool --One Hole--- If not these can also work with elevators or rudder. The woirst thing you can do to keep flying and doing nothing, If so its loss is very likely,

John

Counterweights will always cure flutter....you could even disconnect the surface from the linkage and it won't flutter. But its also true that lighter surfaces and stiffer linkages do help prevent and control flutter.

But what good is a control surface that doesn't flutter if there is no linkage and you can't control the airplane? If your linkage is sloppy and you use counterweights to overcome the flutter it allows, you are only masking the problem and you are left with poor control of the airplane.

There is no one size fits all. Counterweights are great and I highly advocate their use when needed. But tight linkages are a must. I see more cases of flutter due to flex and slop in linkages than any other cause. So when helping someone with flutter problems, I always check and fix linkages first, then add counterweights if needed. The added bonus is that it not only might fix your flutter problem, but it will make your plane fly more accurately.

I'm just trying to let folks know that there is more than one way to skin a cat. Unfortunately, they are all messy

Dave

Clip the ailerons back at the tip. Tapering them back around 2" from the tip, toward the root. This was a trick we used to solve exactly this problem on our fast combat models.

Air gap between the surfaces at the hinge line.

Why do,people make suggestions when they clearly haven't read the entire thread? Counterweights are a Band-aid. Fix the linkage and fix the problem. I'm curious why the OP has not posted pictures?

Looked to me like Scale gave him advise what to do and the problems gone away now.
Intelligent suggestions perhaps not needed.
Heres some good reading on the topic.
http://www.rccr1957.com/flutter.pdf

Sorry Edge, I'm going to dis agree with that article. The two most high performance airplanes in my stable, neither one has ever experienced flutter. Tight linkages and plenty of servo power. The Extra has huge elevators with a single servo, no counterweights, the pylon airplane reaches close to 180 mph. Being semi scale its elevators are a bit larger then on most race airplanes. Each elevator half has its own 65 oz servo and CF pushrod.

You disagree that its some good reading? Nothing was suggested that it was all encompassing and that the cause and solution will be found within.
I do agree with you that tight linkages and plenty of servo torque along with strong gears, preferably metal, will provide suitable control of surfaces.
I've had my own experience with flutter and loss of a plane due to those awful Karbonite gears that Hitec used..

Edge, I should have been more specific. Yes it's a good read but in the bold the author commented that tight linkages were not enough to prevent flutter and that counterbalances must be used. That's the part I couldn't swollow. The article was written around full scale airplanes with manual flight controls. Humans make poor flight control actuators and need balanced controls, models do not.

Heres a tool to help make that calculation.

http://www.mnbigbirds.com/Servo%20To...0Caculator.htm

Interesting, just for giggles I entered the data for the rudder on my Extra and it gave a figure of 492 oz. Way short of what is actually needed. Initially I had a pair of servos that gave 275 oz each. On the ground I had set up a throw of 30 degrees. In the air with full rudder it required slightly over 1/2 throttle to hold knife edge. I changed the servos out to a new pair that are 400 oz each. With the same setup I could now hold knife edge at 1/4 throttle. The original servos just did not have the holding power required.as you can see, I have good mechanical setup, no play or flex from the servos to the tiller.

Flutter tends to show up when flying fast. I have generally seen it on ailerons. You have to go down the list and eliminate all of the variables. Starting with linkages, and flexible surfaces and hinge gap. Those long ailerons on torque rods are the worst. tapering the ailerons back really works. Possibly adding tip plates may as well.